U.S. patent application number 13/917567 was filed with the patent office on 2013-12-19 for method and apparatus of frame scheduling in wireless local area network system.
The applicant listed for this patent is Electronics and Telecommunications Research Institute. Invention is credited to Sok Kyu LEE, Deuk Su LYU, Jae Woo PARK.
Application Number | 20130336250 13/917567 |
Document ID | / |
Family ID | 49755847 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130336250 |
Kind Code |
A1 |
PARK; Jae Woo ; et
al. |
December 19, 2013 |
METHOD AND APPARATUS OF FRAME SCHEDULING IN WIRELESS LOCAL AREA
NETWORK SYSTEM
Abstract
A frame scheduling method performed by a wireless local area
network (WLAN) terminal that transmits a frame in a WLAN system is
provided. The method includes enqueuing a transmission target frame
to a first stage queue corresponding to the transmission target
frame among a plurality of first stage queues generated by
recipient addresses and traffic identifiers (TIDs) of reception
stations, dequeuing, by a first stage scheduler, a first frame from
a queue selected from among the plurality of first stage queues and
transmitting the same to one of a plurality of second stage queues,
and transmitting, by a second stage scheduler, a second frame of a
queue selected from among the plurality of second stage queues.
Inventors: |
PARK; Jae Woo; (Daejeon,
KR) ; LYU; Deuk Su; (Daejeon, KR) ; LEE; Sok
Kyu; (Daejeon, KR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Electronics and Telecommunications Research Institute |
Daejeon |
|
KR |
|
|
Family ID: |
49755847 |
Appl. No.: |
13/917567 |
Filed: |
June 13, 2013 |
Current U.S.
Class: |
370/329 |
Current CPC
Class: |
H04W 72/12 20130101;
H04W 74/0816 20130101; H04W 84/12 20130101 |
Class at
Publication: |
370/329 |
International
Class: |
H04W 72/12 20060101
H04W072/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2012 |
KR |
10-2012-0063319 |
Claims
1. A frame scheduling method performed by a wireless local area
network (WLAN) terminal that transmits a frame in a WLAN system,
the method comprising: enqueuing a transmission target frame to a
first stage queue corresponding to the transmission target frame
among a plurality of first stage queues generated by recipient
addresses and traffic identifiers (TIDs) of reception stations;
dequeuing, by a first stage scheduler, a first frame from a queue
selected from among the plurality of first stage queues and
transmitting the same to one of a plurality of second stage queues;
and transmitting, by a second stage scheduler, a second frame of a
queue selected from among the plurality of second stage queues.
2. The method of claim 1, wherein the plurality of second stage
queues are configured as two or more queues by access categories
(ACs).
3. The method of claim 1, wherein the first frame is selected based
on a channel state by the first scheduler.
4. The method of claim 3, wherein each of the plurality of second
queues includes a plurality of virtual queues.
5. The method of claim 4, wherein the first frame includes timing
information regarding a timing added to any one of the plurality of
virtual queues.
6. The method of claim 5, wherein the second frame is selected
based on the timing information.
7. A wireless terminal performing frame scheduling to transmit a
frame in a wireless local area network (WLAN) system, the terminal
comprising: a processor, wherein the processor is configured to
perform: enqueuing a transmission target frame to a first stage
queue corresponding to the transmission target frame among a
plurality of first stage queues generated by recipient addresses
and traffic identifiers (TIDs) of reception stations; dequeuing, by
a first stage scheduler, a first frame from a queue selected from
among the plurality of first stage queues and transmitting the same
to one of a plurality of second stage queues; and transmitting by a
second stage scheduler, a second frame of a queue selected from
among the plurality of second stage queues.
8. The wireless terminal of claim 7, wherein the plurality of
second stage queues are configured as two or more queues by access
categories (ACs).
9. The wireless terminal of claim 7, wherein the first frame is
selected based on a channel state by the first scheduler.
10. The wireless terminal of claim 9, wherein each of the plurality
of second queues includes a plurality of virtual queues.
11. The wireless terminal of claim 10, wherein the first frame
includes timing information regarding a timing added to any one of
the plurality of virtual queues.
12. The wireless terminal of claim 11, wherein the second frame is
selected based on the timing information.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of Korean
Patent Application No. 10-2012-0063319 filed on Jun. 13, 2012,
which is incorporated by reference in their entirety herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to wireless communications,
and more particularly, to a scheduling method and an apparatus
supporting the same in a wireless local area network (WLAN)
system.
[0004] 2. Related Art
[0005] Recently, diverse wireless communication technologies are
under development in line with the advancement of information
communication technology. Among them, a wireless local area network
(WLAN) is a technique allowing mobile terminals such as personal
digital assistants (PDAs), lap top computers, portable multimedia
players (PMPs), and the like, to wirelessly access the Internet at
homes, in offices, or in a particular service providing area, based
on a radio frequency technology.
[0006] Since IEEE (Institute of Electrical and Electronics
Engineers) 802, a standardization organization of a WLAN technique,
was established in February 1980, a great deal of standardization
works have been conducted.
[0007] The early WLAN technique supported the rate of 1.about.2
Mbps through frequency hopping, spread spectrum, infrared
communications, and the like, by using a 2.4 GHz frequency based on
IEEE 802.11, and recently, a maximum rate of 54 Mbps can be
supported by employing orthogonal frequency division multiplex
(OFDM) technology to the WLAN. Further, IEEE 802.11 are putting
standards of various techniques, such as improvement of quality of
service (QoS), allowing for compatibility of access point (AP)
protocols, achievement of security enhancement, measurement radio
resource measurement, wireless access vehicular environment,
ensuring fast roaming, establishing a mesh network, interworking
with an external network, wireless network management, and the
like, into practical use or are still developing them.
[0008] A basic access mechanism of an IEEE 802.11 MAC (Medium
Access Mechanism) is a CSMA/CA (Carrier Sense Multiple Access with
Collision Avoidance) combined with binary exponential backoff. The
CSMA/CA mechanism is also called a DCF (Distributed Coordination
Function) of IEEE 802.11 MAC, basically employing a `listen before
talk` access mechanism. In this type of access mechanism, a station
(STA) first listens to a radio channel or a medium before starting
a transmission. Upon listening, when it is detected that the medium
is not in use, the listening station starts its transmission.
Meanwhile, when it is detected that the medium is in use, the
station enters a delay period determined by a binary exponential
backoff algorithm, rather than starting its transmission.
[0009] A station which has accessed a channel through the foregoing
channel access procedure may obtain authority to use a wireless
medium and transmit its frame. Here, when a plurality of frames to
be transmitted are buffered in the station, a transmission method
including transmission order of frames is required to be
considered. A scheduling method that may be able to schedule a
transmission schedule of frames and effectively transmit frames in
an opportunity for using a limited wireless medium is required.
SUMMARY OF THE INVENTION
[0010] The present invention provides a two stage scheduling method
capable of solving a performance degradation problem due to a
difference between a time at which information is scheduled in a
higher layer and a time at which a channel is actually
accessed.
[0011] The present invention also provides a wireless device
operable in a wireless local area network (WLAN) system supporting
a two stage scheduling method.
[0012] In an aspect, a frame scheduling method performed by a
wireless local area network (WLAN) terminal that transmits a frame
in a WLAN system is provided. The method includes enqueuing a
transmission target frame to a first stage queue corresponding to
the transmission target frame among a plurality of first stage
queues generated by recipient addresses and traffic identifiers
(TIDs) of reception stations, dequeuing, by a first stage
scheduler, a first frame from a queue selected from among the
plurality of first stage queues and transmitting the same to one of
a plurality of second stage queues, and transmitting, by a second
stage scheduler, a second frame of a queue selected from among the
plurality of second stage queues.
[0013] The plurality of second stage queues may be configured as
two or more queues by access categories (ACs).
[0014] The first frame may be selected based on a channel state by
the first scheduler.
[0015] Each of the plurality of second queues may include a
plurality of virtual queues.
[0016] The first frame may include timing information regarding a
timing added to any one of the plurality of virtual queues.
[0017] The second frame may be selected based on the timing
information.
[0018] In another aspect, a wireless terminal performing frame
scheduling to transmit a frame in a wireless local area network
(WLAN) system is provided. The terminal includes a processor. The
processor is configured to enqueue a transmission target frame to a
first stage queue corresponding to the transmission target frame
among a plurality of first stage queues generated by recipient
addresses and traffic identifiers (TIDs) of reception stations,
dequeue, by a first stage scheduler, a first frame from a queue
selected from among the plurality of first stage queues and
transmitting the same to one of a plurality of second stage queues,
and transmit, by a second stage scheduler, a second frame of a
queue selected from among the plurality of second stage queues.
[0019] According to embodiments of the present invention, a
performance degradation problem arising due to a time difference
between a scheduling timing in an upper layer and a timing for
accessing an actual channel. Frame transmission scheduling
performed in a higher layer may be adjusted by reflecting a
situation at an actual transmission timing. Scheduling information
may be altered by reflecting a channel condition, an access
category (AC) of a frame to be transmitted, and user priority.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a view illustrating a configuration of a wireless
local area network (WLAN) system to which an embodiment of the
present invention is applicable.
[0021] FIG. 2 is a view illustrating an example of a scheduling
method for a frame transmission in the wireless communication
system.
[0022] FIG. 3 illustrates an example of a frame scheduling method
applicable to a WLAN system.
[0023] FIG. 4 illustrates a frame scheduling method according to an
embodiment of the present invention.
[0024] FIG. 5 is a block diagram showing a wireless device to which
an embodiment of the present invention is applicable.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0025] Hereinafter, embodiments of the present invention will be
described in detail with reference to the accompanying drawings. In
describing the present invention, if a detailed explanation for a
related known function or construction is considered to
unnecessarily divert the gist of the present invention, such
explanation will be omitted but would be understood by those
skilled in the art.
[0026] When a component is mentioned as being "connected" to or
"accessing" another component, this may mean that it is directly
connected to or accessing the other component, but it is to be
understood that another component may exist therebetween. On the
other hand, when a component is mentioned as being "directly
connected" to or "directly accessing" another component, it is to
be understood that there are no other components in-between.
[0027] While terms such as "first" and "second," etc., may be used
to describe various components, such components must not be
understood as being limited to the above terms. The above terms are
used only to distinguish one component from another. For example, a
first component may be referred to as a second component without
departing from the scope of rights of the present invention, and
likewise a second component may be referred to as a first
component.
[0028] Also, elements of the embodiments of the present invention
are independently illustrated to show different characteristic
functions, and it does not mean that each element is configured as
separated hardware or a single software component. Namely, for the
sake of explanation, respective elements are arranged to be
included, and at least two of the respective elements may be
incorporated into a single element or a single element may be
divided into a plurality of elements to perform a function, and the
integrated embodiment and divided embodiment of the respective
elements are included in the scope of the present invention unless
it diverts from the essence of the present invention.
[0029] Also, some of the elements may be optional to merely enhance
the performance, rather than being essential to perform a
constitutional function. The present invention may be implemented
by using only the elements requisite for implement the essence of
the present invention, excluding elements used to merely enhance
the performance, and a structure including only the essential
elements excluding the optional elements merely used to enhance the
performance is also included in the scope of the present
invention.
[0030] FIG. 1 is a view illustrating a configuration of a wireless
local area network (WLAN) system to which an embodiment of the
present invention is applicable.
[0031] With reference to FIG. 1, a WLAN system includes one or more
of basic service sets (BSSs). A BSS refers to a set of stations
(STAs) that can communicate with each other in synchronization,
rather than a concept indicating a particular area.
[0032] An infrastructure BSS includes one or more non-AP stations
(non-AP STA1, non-AP STA2, non-AP STA3, non-AP STA4, non-AP STA5),
an access point (AP) providing a distribution service (DS), and a
distribution system connecting the plurality of APs. In the
infrastructure BSS, the AP manages the non-AP STAs of the BSS.
[0033] Meanwhile, the IBSS is a BSS operating in an ad-hoc mode.
The IBSS does not include an AP, so it cannot be a centralized
management entity performing a management function at the center.
Namely, in the IBSS, non-AP STAs are managed in a distributed
manner. In the IBSS, every STA may be configured as a mobile
station, and the IBSS establishes a self-contained network, not
allowing an access to a distribution system (DS).
[0034] A station is a certain function medium including a medium
access control (MAC) and a physical layer interface with respect to
a wireless medium which follow the stipulation of IEEE 802.11
standard. A station includes both AP and non-AP stations in a broad
sense.
[0035] A non-AP STA is an STA which is not an AP. The non-AP STA
may be referred to by other names such as mobile terminal, wireless
device, wireless transmit/receive unit (WTRU), user equipment (UE),
mobile station (MS), mobile subscriber unit, simply, user, or the
like. Hereinafter, a non-AP STA will be designated by STA.
[0036] The AP is a functional entity for providing an access to the
DS by way of a wireless medium for an STA (Associated Station)
associated thereto. In the infrastructure BSS including the AP, in
principle, communications between non-STAs are made by way of the
AP, but when a direct link has been established, the STAs can
directly communicate with each other. The AP may be also called by
other names such as centralized controller, base station (BS),
node-B, base transceiver system (BTS), site controller, and the
like.
[0037] A plurality of infrastructure BSSs including the BSS
illustrated in FIG. 1 may be connected via the DS. The plurality of
BSSs connected via the DS is called an extended service set (ESS).
The AP and/or STAs included in the ESS may communicate with each
other, and a non-AP STA may move from one BSS to another BSS within
the same ESS while seamlessly performing communication.
[0038] In the WLAN system according to IEEE 802.11, a basic access
mechanism of MAC (Medium Access Mechanism) is a CSMA/CA (Carrier
Sense Multiple Access with Collision Avoidance). The CSMA/CA
mechanism is also called a DCF (Distributed Coordination Function)
of IEEE 802.11 MAC, basically employing a `listen before talk`
access mechanism. In this type of access mechanism, an AP and/or
station (STA) senses to a radio channel or a medium before starting
a transmission. As a result of sensing, when it is determined that
the medium is in an idle status, the AP and/or station STA starts a
packet transmission through the corresponding medium. Meanwhile,
when it is detected that the medium is in an occupied state, the
corresponding AP and/or STA does not start its transmission but
sets a delay period for media access and waits.
[0039] The CSMA/CA mechanism includes virtual carrier sensing as
well as physical carrier sensing in which the station (STA)
directly senses a medium. The virtual carrier sensing is to
complement a problem that may arise in media access, such as a
hidden node problem, or the like. For the virtual carrier sensing,
the MAC of the WLAN system uses an NAV (Network Allocation Vector).
The NAV is a value for the AP and/or STA, which currently uses the
medium or has authority to use the medium, to indicate a time
remaining for the medium to be available, to a different AP and/or
STA. Thus, the value set as the NAV corresponds to a period during
which the medium is due to be used by the AP and/or STA which
transmits a corresponding packet.
[0040] Along with a DCF, an IEEE 802.11 MAC provides an HCF (Hybrid
Coordination Function) based on a PCF (Point Coordination Function)
which periodically polls to allow every reception AP and/or STA to
receive a data packet in a synchronous access scheme based on
polling along with the DCF. The HCF has EDCA (Enhanced Distributed
Channel Access) based on contention and an HCCA (HCF Controlled
Channel Access) using a channel access scheme based on
contention-free using a polling mechanism as an access scheme in
which a provider provides data packets to a plurality of users. The
HCF includes a medium access mechanism for enhancing QoS (Quality
of Service) of the WLAN, and QoS data may be transmitted in both of
a contention period (CP) and a contention-free period (CFP).
[0041] FIG. 2 is a view illustrating an example of a scheduling
method for a frame transmission in the wireless communication
system.
[0042] A scheduler selects a queue to be transmitted from a
plurality of queues and transmit data of the corresponding queue.
Here, the plurality of queues may be queues according to types of
data buffered in a single terminal or queues of data buffered in a
plurality of terminals and to be transmitted. In determining to
what degree of data from which queue is to be transmitted, the
scheduler may consider channel information and traffic information.
In transmitting data, beamforming transmission may be performed by
forming and transmitting a beam by applying a precoding matrix, as
necessary.
[0043] A cellular system in which, without channels separated for
each user, several users share a radio channel and a data service
is provided, has a scheduling algorithm for determining to what
degree of data is to be transmitted, to whom data is to be
transmitted, or at which point at present or in the future data is
to be transmitted. In general, an algorithm for checking a state of
channels received by users and selectively transmitting a user
having the best channel condition in a current channel state is
called an opportunistic scheduler or a greedy scheduler. A channel
state, priority, fairness, and the like, may be used as input
factors for determining the scheduling algorithm. As another
example of a scheduling scheme, a scheme of allocating an equal
time to each user by using a round robin algorithm may be used.
[0044] In the cellular-based wireless communication system, the
base station centrally controls allocation of channels to users and
resources, so the centralized scheduling method illustrated in FIG.
2 may be possible. In the WLAN system, an access point (AP) may
serve as a base station as a scheduler in the cellular-based
wireless communication system. An AP may perform scheduling to
allow a particular station (STA) to access a channel and transmit a
frame within a limited range by using a channel access protocol
such as a point coordination function (PCF) or an HCCA (a hybrid
coordination function (HCF) controlled channel access). However,
the PCF or HCCA protocol is inferior to a DCF (distributed
coordination function) or an EDCA (enhanced distributed channel
access) in terms of implementation complexity or stability, so it
is are not frequently used.
[0045] Unlike the cellular system, the WLAN uses a CSMA/CA (carrier
sense multiple access with collision Avoidance), and may use a DCF
or an EDCA protocol as a mechanism for an AP or each STA to
independently access a channel.
[0046] Based on the DCF or the EDCA, every terminal including an AP
or an STA equally access a channel through a CSMA/CA. The CSMA/CA
protocol uses a random backoff method, having non-deterministic
characteristics as to when a STA will be allocated a channel. Due
to this characteristics, when a channel is quickly changed, it is
difficult to obtain a scheduling gain.
[0047] The WLAN system may be divided into a lower layer portion
including the DCF or the EDCA that may be largely implemented by
hardware and a higher layer that has a function of enqueuing a
frame to a queue by access categories (ACs) and performs a
management function. The higher layer may also be implemented by
software.
[0048] FIG. 3 illustrates an example of a frame scheduling method
applicable to a WLAN system.
[0049] In a WLAN system, there may be two stage queue. An upper
layer may perform first stage queuing to set a queue in
consideration of an STA and a TID parameter, and dequeue a frame
from a first stage queue generated through the first stage queuing
in consideration of a size that can be aggregated into a single
transmission frame, a channel state, and the like, and transmit the
same to a queue by ACs.
[0050] In a second stage queue, a queue by ACs is selected by the
EDCA protocol in input order, and a frame present in a header of
the queue may be transmitted.
[0051] As shown in the example of FIG. 3, when scheduling is
applied in the WLAN system, in general, scheduling is implemented
in a higher layer in consideration of complexity of the system. The
higher layer may receive traffic information including channel
information and user priority information from each STA and enqueue
data corresponding to an appropriate STA to queue by ACs.
[0052] The queue by ACs may be randomly selected by the DCF or
EDCA. Data may be transited to a wireless medium according to a
method of FCFS (First Come, First Served) in which frame which
first arrived from a queue is first transmitted.
[0053] In this method, although the higher layer determines order
of data in consideration of a channel state and inputs it in the
second stage queue to inform it, data may not be transmitted in a
designated time due to the characteristics of the CSMA/CA
protocol.
[0054] Thus, there may be a time difference between a timing at
which a channel state is determined considered to determine a queue
in the higher layer and a timing at which actual data is selected
and transmitted through a wireless medium. The difference between a
reference timing of the channel state referred to for setting a
queue in the high layer and the timing at which data is actually
transmitted may cause a degradation of transmission efficiency in a
certain portion. This is because information such as a channel
state, or the like, referred to for setting a transmission queue
may be different from information such as a channel state, or the
like, at a timing at which data is actually transmitted. As the
time difference between both timings as described above is
increased, the possibility that performance degradation appears may
also be increased.
[0055] In a different method of a frame transmission, data may be
extracted midway without using the FCFS scheme, but this method may
cause a problem that information regarding order of packets
received by a receiver, and the like, may be additionally
required.
[0056] In the example of FIG. 3, the queue separated in two stages
may be conceptually integrated into one, but it may be difficult to
be implemented in an actually applied embodiment.
[0057] FIG. 4 illustrates a frame scheduling method according to an
embodiment of the present invention.
[0058] The frame scheduling method according to an embodiment of
the present invention may use two stage scheduling. In a first
stage queue, each queue may be generated for each RA (Receiver
Address) and TID (traffic identifier). The two stage queue may be
configured as two or more queues in each AC.
[0059] In order to enhance data transmission efficiency in the WLAN
system, when frames received from a higher application have the
same reception STA and TID, a frame aggregation method of reducing
overhead of a channel access by increasing a size of frames may be
applied. Namely, when a plurality of frames transferred from the
higher layer are frames to be transmitted to the same station and
TIDs of the frames are identical, the plurality of frames may be
aggregated so as to be transmitted in the form of an A-MSDU.
[0060] In the first stage, queues may be manages by STAs and TIDs.
A first stage schedule may predict a size of aggregated frames and
channel information to select a queue having a good channel state
among queues in which the number of frames stored therein exceeds
an aggregation size. The channel stage may be obtained by
observing/predicting a channel state, and may also be obtained
through feedback from reception terminals.
[0061] When the channel state is the same, a queue having high
priority to which TID is mapped may be selected. Data from the
selected first stage queue may be dequeued and sent to the second
stage queue.
[0062] When the first stage scheduler enqueues the frame from the
queue selected in the first stage to two or more queues, the first
stage schedule may select a queue in the following manner. In IEEE
802.11e, an AC mapped according to a TID value is designated. Here,
when a new frame is mapped to a queue by ACs by a TID, two or more
queues may exist in the AC, and a frame to be transmitted may be
selected according to the following rule.
[0063] A queue to which a frame having the same information
previously is selected as a two stage queue. Here, in order to
prevent concentration of traffic to one side, a position of the
first stage schedule may be changed. The first stage scheduler may
check an amount of traffic and select a virtual queue number within
an AC from RA and TID by using additional mapping information. An
enqueue time at which the scheduler determines channel information
after the queue is selected may be recorded as information
regarding a frame. Information regarding the frame may be a buffer
descriptor, specifically, a TxBD (Transmission Buffer Descriptor).
Here, TxBD is transmitted together with a frame and includes
information regarding how a frame is to be processed. An enqueue
timing may be included in the TxBD and transmitted together with
the frame. Here, as the recorded enqueue timing, a timing at which
the scheduler determines that a channel is good is recorded.
[0064] The first stage scheduler may store at least any one of
whether to apply beamforming, aging information of a beamforming
matrix, and user priority information together with information
indicating an enqueue timing.
[0065] Hereinafter, an example of a method for selecting a queue by
the second stage scheduler will be described. The two stage
scheduler may independently select a virtual queue by ACs. A
channel access function of the WLAN system has one exposed queue by
ACs. A plurality of virtual queues may be configured in the exposed
queue. Information regarding the virtual queues is integratedly
managed such that virtual queues belonging to the same AC are
viewed as a single exposed queue in view of the EDCA block. Since
the EDCA block only need to know whether or not there is a frame in
the exposed queue, when even one frame exists in the virtual queue,
the two stage scheduler informs the EDCA block that there is a
frame in the exposed queue.
[0066] The exposed queue by ACs is selected by the EDCA protocol,
and the two stage scheduler may select a virtual queue from a
plurality of virtual queues corresponding to a selected AC
according to the following procedure.
[0067] The two stage scheduler may retrieve information of a frame
existing in a header of each virtual queue and compare them to
select a queue. In case of a transmission to which beamforming is
applied, aging information of channel information is checked.
Namely, how long before the channel information was updated is
checked, and a frame having old channel information may be selected
or a frame having the latest information may be selected according
to a scheduling policy.
[0068] When beamforming is not applied to all the frames present in
the header of the virtual queue, a frame having the earliest
enqueue timing may be selected or a frame included in the latest
queue may be selected.
[0069] When an enqueue timing is within a pre-set range according
to the scheduling policy, a frame to be transmitted to an STA
having highest priority in consideration of priorities of STAs may
be selected.
[0070] A frame is dequeued from the selected queue according to the
foregoing algorithm and transmitted to a wireless medium (WM).
[0071] In case of one virtual queue, a frame may be transmitted
according to an FCFS policy. In case of two or more virtual queues,
a method such as round-robin, or the like, may be used, and an
employed policy/scheme may vary according to a scheduling
policy.
[0072] FIG. 5 is a block diagram showing a wireless device to which
an embodiment of the present invention is applicable. A wireless
device 70 is an STA that may implement the foregoing embodiment,
which may be an AP or a non-AP station.
[0073] The wireless device 70 includes a processor 72, a memory 74,
and a transceiver 76. The transceiver 76 transmits/receives a radio
signal and implements a physical layer of IEEE 802.11. The
processor 72 is functionally connected to the transceiver 76 to
implement a MAC layer and a physical layer of IEEE 802.11. The
processor 72 may be configured to implement the two stage
scheduling scheme proposed by the present invention, thus
implementing the foregoing embodiments.
[0074] The processor 72 and/or transceiver 76 may include an ASIC
(application-specific integrated circuit), a different chip set, or
a logical circuit and/or data processing unit. The memory 74 may
include a ROM (read-only memory), a RAM (random access memory), a
flash memory, a memory card, a storage medium and/or any other
storage devices. When an embodiment is implemented by software, the
foregoing scheme may be implemented as a module (process, function,
etc.) performing the foregoing function. The module may be stored
in the memory 74 and executed by the processor. The memory 74 may
be present within or outside the processor 72 and may be connected
to the processor through various known units.
[0075] While the present invention has been shown and described in
connection with the embodiments, it will be apparent to those
skilled in the art that modifications and variations can be made
without departing from the spirit and scope of the invention as
defined by the appended claims.
* * * * *